Two-stroke internal-combustion engine



June 19,1928, 1,674,571

J. ROM EYN 1W0STROKE INTERNAL COMBUSTION ENGINE Filed May 1, 1926 nzfwn Patented June l9,v 1928.

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Application filed May -1, I926, Serial No.'106,04;5,- and"in Great-BritainMay 18, 1925.

nal ports. In such engines, as constructed up to n'oW ,'-the additlonal scavenging valve mechanically or by a r is operated either pressure.

"Vhen the valve is mechanically operated, the engine loses the; remarkable -simplic ity which is one of the advanta es ottwo str'oke On the other port "scavenging engines. I hand, when the valve opens under the working of the airpressure, it is liable to be,

noisy in operation, especially in large engines. v 7

In the engine according to this invention, there is a scavengingpump, which is designed to feed only the small scavenging valves fitted to the combustion'chambers of the various cylinders. This scavenging pump works at a pressure substantially high er than the pressure of the main scaveng ng air, sothat a. small auxiliary scavenging total quantity of scavenging air, and'i's large .ly compensated by the advantage of having- I 40 a r valve is suflicientto fill the combustionchamber in the short time available." Of course, the increase in pressure of a part of the scavenging air means a loss of power, but this loss only affects a small part of the a small scavenging valve.

When the pressure ofthe opening of these valves is lengthened to- Wards the end of thecompression. The! consequence thereof is-that a certain part of the scavenging "air enters :the cylinder after the closing of the exhaust ports. This fact can be made use otn-forsupercharging,

if the deliveryof the auxiliary scavenging pump is increased accordingly. But as the compression of the air in the auxiliary scavenging pump uses more powerthan compression in the main scavenging pump, it

' will be generally more advantageous to avoid any superchargingefiect, and to shorten the I scavenging air I entering the cylinders throughthe auxiliary scavenging valves is increased, the period 0t period during'wliich the. scavenging air enters the combustion chamber. Therefore,

according to the invention, a vsmallreservoirmay beiprovided imn'iediatelyin front of' theqauxiliar-y scaveiiging valve of each combustion chamber and this reservoir is fed from :the' scavenging pump through, a

small opening.

,In this Way, when the pressure at the end of-theexpansion "drops below the pressure of the auxiliary sciaven gin g air, the scaven 111g valve'opens, and the aircontained'in the aforesaid reservoir scavenges-the combustion chamber. r

The pressure in the reservoir however drops very quickly, andthe quantity of air supplied to the combustion chamber 'ait'ter this rush of, airfinto it, only the small quantity. which can pass through the small opening betweeri tlie j punip and, the reser An embodiment of the invention is represented diagrammatically by Way of example in vertical section in the accompanying drawing. a is the cylinder of the' engine, I) the piston thereof, 0 represents one of the] scavenging ports, and a one portsg Combustion takes place-in the chamber f, which is in communication with the main of the exhaust cylinder through the restricted passage'g, h f 7 is an injector of any known construction and 7 .z' the auxiliary scavenging valve, which opens inwardly and is kepton, its seatby meansof the spring j. represents the cylinder of the scavenging pump, Us the piston thereof, and'm' and n are't-he suction and ties livery valves; The scavenging pump k delivers "air at a pressure P substantially higher thanthe pressure P of the main scavenging air, throughthe small opening 0 into the reservoir p. At the end of theexpansion stroke, when the exhaust portse are opened,

thepressure in the main cylinder drops rapidlyiand when it becomes less than the pres sure P, the valve opens, and the air contained in the reservoir p (rushes into the combustion chamber f and expels the burnt gases contained therein. 'In the meantime, scavenging takes place inthe main cylinder through the ports 0, and: the burnt gases expelled from-the combustion chamber 7 are thereafter expelled from the main cylinder also by the scavenging air entering through the ports a. The volume of the reservoir 7) is such that the pressure in it and inthe combustion chamber f is substantially equalized with the pressure in the main cylinder, be fore the exhaust ports 0 are closed. Consequently, when the ports 6 are closed and compression starts, the valve 2' is closed, and

.the pressure in the reservoir p iiicreases gradually up to the pressure P.

It is also possible to avoid the use of the reservoir 39, but then the valve 2' closes later, i. e. when the pressure in the cylinder becomes equal to the pressure P of the auxiliary scavenging air. As it is necessary that the burnt gases ber before the process of scavenging is linished in the main cylinder, it is then necessary to make the delivery of the pump 70 substantially larger than would be required for filling only the combustion chamber with fresh air, and the power required for driving the pump is larger. On the other hand, there is a certain super charging which in creases the'power which is produced by the cylinder.

lVhat I claim is:

1. In an internal combustion engine, a cylinder; a piston working therein; a combustion chamber at one end of the cylinder; a restricted passage providing communication between the chamber and cylinder; said be expelled from the eha. m

cylinder having a scavenging air inlet and an outlet which are opened by said piston near the end of its power stroke; a reservoir for auxiliary scavenging air; a duct leading from said reservoir to the combustion chamher; a normally closed valve controlling communication between said duct and said chamber; and meansfor feeding air to the reservoir at a pressure substantially higher tnan the pressure in the cylinder.

2. In an internal combustion engine, a cylinder; a piston working therein; a combustion chamber at one end of the cylinder; a restricted passage providing communication between the chamber and cylinder; said cylinder having a scavenging aininlet and and outlet which are opened by saidpistou near the end oi its power stroke; a reservoir for auxiliary scavenging air; a duct leading from said reservoir to the combustion chamber; a normally closed valve controlling communication between said duct and said chamber; and means for feeding air to, the reservoir at a pressure substantially" higher than the pressure in the cylinder, said reservoir having a small inlet orifice to ad mit such air. I

In testimony whereofI affix my signature.

JEAN'ROMEYN. 

